How Autonomous Cars Will Change Traffic

AutoVots and TaxiBots on the virtual streets of Lisbon

International Transport Forum

TaxiBots and AutoVots may sound like toys that you played with in the 1980s that have been turned into a blockbuster movie franchise. They're actually autonomous vehicle concepts used in a study released in April by the Organization for Economic Cooperation and Development. Scientists wanted to plug virtual self-driving vehicles into a model of a real, live city using the data from a day of traffic and see what happened. It turns out, what happens is you free up a lot of paved space that can be used for recreation or buildings.

Neither of the concepts are modeled on privately owned cars. The AutoVots were set to pick up and drop off one passenger at a time in a car-sharing system, similar to Zipcar or Car2Go. TaxiBots, as you probably guessed, worked like taxis, with several passengers at a time sharing a ride. A central “mobility dispatcher” would decide if an AutoVot or TaxiBot would be the most efficient, time-wise. (Since researchers didn’t specify what kind of engine the cars had, fuel efficiency wasn’t part of the study.)

The city in the model wasn’t some extra-planetary wonderland; researchers used real data from Lisbon, Portugal. There were two important rules in the study: First, there had to be just as many trips made by the virtual, autonomous cars as by real-world vehicles, and they should take just as long and go to the same places as the trips in the Lisbon data. Second, all trips in the virtual Lisbon were to be made in AutoVots and TaxiBots. No buses or private cars driven by humans allowed. Scientists did make room in the system for light rail or commuter rail, though.

What the researchers found was that it took 90 percent fewer autonomous cars to accomplish the same trips as the human-piloted vehicles on the road in Lisbon today. If a city is without light rail, that number is still high, with 80 percent fewer vehicles required to get everybody around. Beyond any environmental benefits, the study found that 80 percent of off-street parking could be removed and streets could be 20 percent narrower.

The downside is that taking away buses and using AutoVots means there are a lot more cars on the road--about 20 percent more during the peak morning commute hours. When the simulation was run with TaxiBots, the increase was 5 percent or less. Sharing is caring, everyone. And less congested.